1. Field of the Invention
This invention relates to a filter unit for an image forming apparatus such as a photocopier, a printer and the like.
2. Description of Related Art
An intake and an exhaustion of internal and external air stream are performed by an image forming apparatus such as a photocopier of an electro-photographic type, a printer, a facsimile machine for a purpose of thermal fixation of an image and also for a purpose of cooling. An exhaust opening and an intake opening of most image forming apparatuses are prepared with an electrostatic filter for dust prevention.
A conventional structure of the electrostatic filter will hereinafter be described with reference to FIG. 7 through FIG. 9. FIG. 7 shows a conventional electrostatic filter unit, FIG. 8 shows a conventional electrostatic filter, and FIG. 9 shows a filter casing.
An electrostatic filter unit 100 shown in FIG. 7 is prepared to an air duct 102 formed with an electric power cord 105 and a blower 101, e.g., a fan in which the air duct 102 guides air created by the blower 101 to a targeted member subject to internal blowing. In means to prevent dust or the like from entering the targeted member subject to internal blowing, an electrostatic filter 103 is contained within a filter casing 106 and is engaged to either the blower 101 or the air duct 102. An upper lid 104 having plural ventilation openings and serving as a safety member for preventing the user from directly touching the blower 101 is engaged to the blower 101 or the air duct 102 on a downstream side of the electrostatic filter 103. Synchronizing with the operation of an apparatus body, when power is supplied via the electric power cord 105, the blower 101 rotates and the, in the direction illustrated in arrow A, air from outside containing dust or the like enters an intake opening and passes through the electrostatic filter 103 and then enters the air duct 102 and continues to enter the inside of the image forming apparatus.
As shown in FIG. 8, the electrostatic filter 103 is formed in a corrugated shape for effective dust removal and pressure loss reduction, and for the purpose of maintaining thus corrugated shape, an edge portion of creasings of the filter is secured by a fixing means such as a hot-melt type adhesive 107.
Nevertheless, due to a manufacturing problem of the hot-melt type adhesive 107 and also due to a heating problem caused from a processing of the hot-melt type adhesive 107, the structure in which the hot-melt type adhesive 107 securing the edge portion of the creasings of the electrostatic filter creates extreme difficulty in a case such as achieving a precise measurement. Accordingly, the structure raises a problem of requiring a large number of processing steps. Furthermore, the electrostatic filter 103 tends to deform extremely easily and is difficult to be solely used regardless of the fact that both sides of the electrostatic filter 103 are secured by the hot-melt type adhesive 107; therefore, in order to actually use the electrostatic filter 103, the electrostatic filter 103 requires to be contained in a filter casing 106 shown in FIG. 9 or a casing of the like and also requires much labor in a manufacturing process.
Thus conventional structure required the upper lid 104 at a downstream portion of the electrostatic filter 103 for a safety measure in which the upper lid 104 is provided with a louver or louvers serving as ventilation openings; further, with thus conventional structure a space inside the image forming apparatus would become necessary and also the processing steps for maintenance would increase in correspondence with the increase in the number of components. Many image forming apparatuses such as photocopiers, facsimiles, or printers are structured in a manner where a fan motor and the like could easily be touched during use or during maintenance; therefore, a prevention of thus touching of the fan motor and the like would be necessary.
The object of this invention is to provide a filter unit to be easily manufactured with high component precision. Another object of this invention is to provide a highly durable filter unit. Another object of this invention is to provide a filter unit having: a corrugated filter; a casing for containing the filter; and a reinforcement member formed by casting a resin material into one recess of the filter at least. A further object of this invention will be described hereinafter.